Nonlinear dynamics and band transport in a superlattice driven by a plane wave.

A quantum particle transport induced in a spatially periodic potential by a propagating plane wave has a number of important implications in a range of topical physical systems. Examples include acoustically driven semiconductor superlattices and cold atoms in an optical crystal. Here we apply a kinetic description of the directed transport in a superlattice beyond standard linear approximation, and utilize exact path-integral solutions of the semiclassical transport equation. We show that the particle drift and average velocities have nonmonotonic dependence on the wave amplitude with several prominent extrema. Such nontrivial kinetic behavior is related to global bifurcations developing with an increase of the wave amplitude. They cause dramatic transformations of the system phase space and lead to changes of the transport regime. We describe different types of phase trajectories contributing to the directed transport and analyze their spectral content.

Subterahertz chaos generation by coupling a superlattice to a linear resonator.

We investigate the effects of a linear resonator on the high-frequency dynamics of electrons in devices exhibiting negative differential conductance. We show that the resonator strongly affects both the dc and ac transport characteristics of the device, inducing quasiperiodic and high-frequency chaotic current oscillations. The theoretical findings are confirmed by experimental measurements of a GaAs/AlAs miniband semiconductor superlattice coupled to a linear microstrip resonator. Our results are applicable to other active solid state devices and provide a generic approach for developing modern chaos-based high-frequency technologies including broadband chaotic wireless communication and superfast random-number generation.

[Implantation of stent- graft because of aorta rupture in polytrauma].

The article describes the clinical case and analyzes the literature concerning endoprosthesis replacement in the case of traumatic thoracic aortic injury in polytrauma. Current strategy of diagnostics and treatment of patient in critical condition with rupture of isthmic aortic part is based on the principle of multistage surgical treatment (damage control orthopedic). The external fixation of multiple pelvis and extremities fractures and on-time implantation of stent-graft in thoracic aortic part were performed at first hours after the admission. A condition of the patient was stabilized. The delayed reconstructive operations on pelvis and extremities bones allowed obtaining the satisfactory functional result. The principles of staged surgical treatment and the use of on-time high-technology methods allowed saving life for the patient even in critical situation in I level traumatologic centre.

Rectification of terahertz radiation in semiconductor superlattices in the absence of domains.

We study theoretically the dynamical rectification of a terahertz AC electric field, i.e. the DC current and voltage response to the incident radiation, in strongly coupled semiconductor superlattices. We address the problem of stability against electric field domains: a spontaneous DC voltage is known to appear exactly for parameters for which a spatially homogeneous electron distribution is unstable. We show that by applying a weak direct current bias the rectifier can be switched from a state with zero DC voltage to one with a finite voltage in full absence of domains. The switching occurs near the conditions of dynamical symmetry breaking of an unbiased semiconductor superlattice. Therefore our scheme allows for the generation of DC voltages that would otherwise be unreachable due to domain instabilities. Furthermore, for realistic, highly doped wide miniband superlattices at room temperature, the generated DC field can be nearly quantized, that is, be approximately proportional to an integer multiple of hω/ea where a is the superlattice period and ω is the AC field frequency.